How much protein do athletes really need?

Protein is one of the most talked-about nutrients in sport. It is also one of the easiest to oversimplify. On one side, there is the old-school view that as long as athletes meet the recommended daily allowance, they are covered. On the other side, there is the modern marketing version: more protein, more often, from more products, must always be better. Neither view really captures the science.

Minimum versus optimal protein intake

When athletes ask, “How much protein do I need?”, they are usually not asking about survival. They are not interested in the minimum intake needed to prevent deficiency. They want to know how much protein will best support recovery, adaptation, training quality, and ultimately performance. That is a different question entirely. We need to distinguish between a protein requirement and a protein recommendation. A requirement refers to the minimum intake needed to meet basic metabolic needs. A recommendation for athletes is about optimising the response to training.

That distinction matters, because the commonly quoted recommended daily allowance (RDA) of 0.8 g/kg/day was never designed for athletes trying to maximise muscle reconditioning. It came from nitrogen balance work aimed at estimating minimum needs in the general population. In that context, it makes sense. In sport, it is often the wrong target.

Protein digestion, absorption, and utilisation

Before deciding how much protein athletes need, it helps to understand where that protein goes. Protein is digested into amino acids and small peptides, absorbed in the small intestine, and released into the bloodstream. From there, amino acids have several possible fates. They can be used to build body proteins, including muscle proteins. They can be oxidised for energy. Or their nitrogen can be excreted, mainly as urea. In other words, not every gram of protein eaten ends up as muscle. This is why simply eating more protein does not guarantee more adaptation. The key issue is not just intake, but what proportion of that intake actually stimulates muscle protein synthesis.

Simply eating more protein does not guarantee more adaptation. The key issue is not just intake, but what proportion of that intake actually stimulates muscle protein synthesis.

The response depends on blood amino acid availability, delivery of amino acids to muscle, uptake into muscle, and the intracellular signalling processes that switch protein synthesis on, especially the mTOR pathway. Leucine gets particular attention because it is not just a building block, but also an important signal. If these processes are optimised, the muscle protein synthetic response can be maximised.

Why 20 grams of protein became the magic number

For years, the broad consensus in sports nutrition was that around 20 g of high-quality protein after exercise was enough to maximise muscle protein synthesis.

That idea did not appear out of nowhere. It came from a series of elegant dose-response studies in young resistance-trained men. In one of the classic studies, egg protein was given in doses up to 40 g after leg-only resistance exercise (1). Muscle protein synthesis increased up to 20 g, but there was no further rise at 40 g. Witard and colleagues then saw a similar pattern using whey protein where muscle protein synthesis increased from 0 to 10 to 20 g, but 40 g did not add anything extra in the setting of leg only resistance exercise (2). Instead, more amino acids were oxidised or excreted. That led to a simple message: 20 grams of protein is plenty. It was a useful message, but it was never the whole story.

The problem with universal protein advice

Science has a habit of punishing overly simple rules, and protein is no exception.

More recent studies challenged the idea that there is a hard ceiling at 20 g. A particularly influential study from Maastricht used whole-body resistance exercise and compared 25 g with a very large 100 g dose of protein (3). Over a prolonged recovery period, the larger dose increased both the magnitude and duration of the muscle protein synthetic response.

In a study led by Lindsay Macnaughton where participants performed whole-body resistance exercise, 40 g of whey protein was found to stimulate muscle protein synthesis more than 20 g (4).This does not mean that everyone now needs 100 g of protein after training. It means context matters. The original 20 g studies mostly used leg-only exercise in young men. When the amount of muscle activated is greater, the dose needed to maximise the response may also be greater. So instead of asking, “Is 20 g enough?”, the better question becomes, “Enough for what, and for whom?”.

A smarter way to think: protein relative to body mass

Absolute recommendations are convenient, but athletes are not all the same size.

A 50 kg gymnast, an 80 kg footballer, and a 110 kg rower should probably not all receive the same protein advice. To address this, researchers pooled dose-response data and expressed protein intake relative to body mass (5). The outcome was one of the most useful practical recommendations in modern sports nutrition: about 0.24 g/kg per serving on average, with 0.30 g/kg per serving as a practical upper target to cover variation between individuals.

• a 50 kg athlete may need around 15 g

• a 70 kg athlete around 21 g

• a 100 kg athlete around 30 g

This is much more useful than repeating “20 grams” to everyone regardless of size, sport, and training session.

Does exercise type matter?

Resistance exercise and endurance exercise do not stress muscle in exactly the same way, and the protein targets may not be identical. In the lecture, Witard discusses evidence showing that after endurance exercise, around 30 g of protein was sufficient to maximise both myofibrillar and mitochondrial protein synthesis in trained young men. That is interesting, because it suggests endurance athletes should not think of protein as something mainly relevant to strength athletes. Protein also supports the remodelling that underpins endurance adaptation.

There is also emerging evidence that sex may matter. In one study of resistance-trained females performing whole-body resistance exercise, 30 g of whey was sufficient to maximise muscle protein synthesis (6). That does not mean female athletes need less protein in all situations, but it is a reminder that data from young men cannot always be copied directly into every population.

Daily vs per-meal protein intakes

Per-meal dosing is useful, but athletes live across days and weeks, not just around one shake. For athletes in energy balance and trying to support recovery and adaptation, the general consensus remains around 1.3 to 1.6 g/kg/day, with 1.6 g/kg/day often presented as a solid evidence-based target for maximising training adaptation in weight-stable individuals. Intakes much higher than this do not appear to further increase hypertrophy under weight-stable conditions.

That is an important point because it pushes back against the idea that more protein is always better. For many athletes, once total daily intake is in the right range and individual meals are well distributed, piling on extra protein is unlikely to produce extra gains.

Is more protein better during weight loss?

This is where the evidence supporting higher protein intakes become more convincing. Not all athletes want to maintain weight all year-round. Some need to make weight. Some want to improve power-to-weight ratio. Some are in phases where fat loss is the goal. In that context, preserving lean mass becomes critical.

Context is everything. The best protein recommendation depends on whether the athlete is weight stable, trying to gain, or trying to lose weight.

During energy restriction, higher protein intakes help athletes retain muscle while losing fat. In men, a protein intake of around 2.4 g/kg/day during a large energy deficit helped preserve lean mass far better than a more moderate intake (7). Similar findings were seen in women, with higher protein intakes helping retain muscle mass while still allowing fat loss (8). So when the goal is high-quality weight loss, the recommendation shifts upwards to around 2.0–2.4 g/kg/day. Again, context is everything. The best protein recommendation depends on whether the athlete is weight stable, trying to gain, or trying to cut.

Debunking myths around kidney function and bone health

Athletes still hear that high protein diets damage the kidneys or harm bone health. As Witard makes clear, that concern is not supported in healthy individuals. Clinical populations with kidney disease are a different matter, but for healthy athletes, there is no good evidence that high protein diets are inherently harmful. In fact, the lecture points out that the idea of high protein intakes being dangerous for healthy athletes simply does not stand up to scrutiny. That does not mean athletes should eat huge amounts of protein for no reason. It means the argument against higher intakes should be based on the lack of added benefit in some contexts, and not on fear.

Summary

So where does all this leave us? First, athletes should stop using the RDA as a performance target. That number was never built for them. Second, the old “20 grams is enough” rule was useful, but it is too simplistic. Protein dose should depend on body mass, the type of exercise, and the training goal. Third, a sensible working target is around 0.3 g/kg per meal and around 1.6 g/kg/day for most weight-stable athletes. Fourth, when athletes are in an energy deficit and want to preserve muscle while losing fat, protein needs are likely higher, in the range of 2.0 to 2.4 g/kg/day. And finally, more is not always better. But sometimes more is justified. That is the real message. Not hype. Not fear. Just context.

References

1. Moore, D.R., Robinson, M.J., Fry, J.L., Tang, J.E., Glover, E.I., Wilkinson, S.B., Prior, T., Tarnopolsky, M.A. and Phillips, S.M. (2009) ‘Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men’, The American Journal of Clinical Nutrition, 89(1), pp. 161–168. doi: 10.3945/ajcn.2008.26401.

2. Witard, O.C., Jackman, S.R., Breen, L., Smith, K., Selby, A. and Tipton, K.D. (2014) ‘Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise’, The American Journal of Clinical Nutrition, 99(1), pp. 86–95. doi: 10.3945/ajcn.112.055517.

3. Trommelen, J., van Lieshout, G.A.A., Nyakayiru, J., Holwerda, A.M., Smeets, J.S.J., Hendriks, F.K., van Kranenburg, J.M.X., Zorenc, A.H., Senden, J.M., Goessens, J.P.B., Gijsen, A.P. and van Loon, L.J.C. (2023) ‘The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans’, Cell Reports Medicine, 4(12), article 101324. doi: 10.1016/j.xcrm.2023.101324.

4. Macnaughton, L.S., Wardle, S.L., Witard, O.C., McGlory, C., Hamilton, D.L., Jeromson, S., Lawrence, C.E., Wallis, G.A. and Tipton, K.D. (2016) ‘The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein’, Physiological Reports, 4(15), article e12893. doi: 10.14814/phy2.12893.

5. Moore, D.R., Churchward-Venne, T.A., Witard, O., Breen, L., Burd, N.A., Tipton, K.D. and Phillips, S.M. (2015) ‘Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men’, The Journals of Gerontology: Series A, Biological Sciences and Medical Sciences, 70(1), pp. 57–62. doi: 10.1093/gerona/glu103.

6. Mallinson, J.E., Wardle, S.L., O’Leary, T.J., Greeves, J.P., Cegielski, J., Bass, J., Brook, M.S., Wilkinson, D.J., Smith, K., Atherton, P.J. and Greenhaff, P.L. (2023) ‘Protein dose requirements to maximize skeletal muscle protein synthesis after repeated bouts of resistance exercise in young trained women’, Scandinavian Journal of Medicine & Science in Sports, 33(12), pp. 2470–2481. doi: 10.1111/sms.14506.

7. Mettler, S., Mitchell, N. and Tipton, K.D. (2010) ‘Increased protein intake reduces lean body mass loss during weight loss in athletes’, Medicine & Science in Sports & Exercise, 42(2), pp. 326–337. doi: 10.1249/MSS.0b013e3181b2ef8e.

8. Pearson, A.G., Alexander, L., Witard, O.C., Coughlin, T.E., Tipton, K.D. and Walshe, I.H. (2021) ‘A hypoenergetic diet with decreased protein intake does not reduce lean body mass in trained females’, European Journal of Applied Physiology, 121(3), pp. 771–781. doi: 10.1007/s00421-020-04555-7.